Researchers reporting online in the journal Cell, a Cell Press publication, have found another good reason to eat your green vegetables, although it may or may not win any arguments with kids at the dinner table.

It turns out that green vegetables -- from bok choy to broccoli -- are the source of a chemical signal that is important to a fully functioning immune system. They do this by ensuring that immune cells in the gut and the skin known as intra-epithelial lymphocytes (IELs) function properly.